and Bulgarian CHERNOYE MORE, Ukrainian CHORNE MORE, Turkish KARADENIZ,
Romanian MAREA NEAGRA, large inland sea situated at the southeastern extremity
of Europe. It is bordered by Ukraine to the north, Russia to the northeast,
Georgia to the east, Turkey to the south, and Bulgaria and Romania to
The Black Sea is connected to the distant waters of the
Atlantic Ocean by the succession of the Bosporus (a strait at
the Black Sea's southwestern corner), the Sea of Marmara, the Dardanelles,
the Aegean Sea, and the Mediterranean Sea.
The peninsula of Crimea extends into the sea from the north, and immediately to the east
the narrow Kerch Strait opens onto the smaller Sea of Azov. The Black Sea's water-surface
area is about 178,000 square miles (461,000 square km), and its maximum depth is more than
7,250 feet (2,210 m). The Black Sea has few coastal lowlands. The Danube, Dnieper,
Dniester, and Don are the largest rivers emptying into the sea.
The Black Sea is a residual basin of the ancient Tethys
Sea; its present form probably emerged about 58 million years ago when structural
upheavals in Anatolia split off the Caspian basin from the Mediterranean. The newly formed
Black Sea basin gradually became isolated from the ocean, its salinity was reduced, and it
was slowly separated from the Caspian region. The salinity of the Black Sea is
almost half that of the world's oceans.
An unusual feature of the Black Sea is that oxygen is
dissolved only in the upper levels of its waters, which alone can support a rich sea life
as a result. Below a depth of 230-330 feet (70-100 m) at the centre and 330-500 feet
(100-150 m) near the sea's margins, there is no oxygen because the sea is permeated by a
high concentration of dissolved hydrogen sulfide, forming a saturated, "dead"
zone inhabitable only by specially adapted bacteria. Despite this anomaly, the Black Sea's
uppermost waters supported abundant sturgeon, mackerel, and anchovy until the late 20th
century, when the runoff of industrial and municipal wastes into the Danube, Dnieper, and
other feeder rivers caused increasing levels of pollution and consequent reductions in
The Black Sea remains an important shipping artery linking
Ukraine, Bulgaria, Romania, and southwestern Russia with world markets. The sea's northern
coast, particularly the Crimea, is a major recreational area for eastern European